Seeking advice regarding hard clunk from transmission

[Faheem_23]

I'm looking for advice on my 2018 Mazda CX-5 (FWD, 129k miles) regarding a concerning 'hard clunk' I feel during gear changes at low RPMs (1,000–1,500 range), particularly in stop-and-go traffic. Additionally, during cold starts in the morning, the car violently jerks/lunges forward the very first time I apply the brakes while moving. The transmission fluid is likely original, as the dealer confirmed they did not change it during their recent service. I'm trying to determine if this is a known TCM software/logic issue (like TSB 05-006/24), a sign of worn transmission mounts, or if I should risk a drain-and-fill on original fluid at this high mileage to resolve the shift shock. Has anyone else with a high-mileage Gen 2 CX-5 dealt with this combination of symptoms, and did a software flash or fluid refresh actually fix it?

 

[dan25man]

I mean i have a 2014 with 131k miles and the original transmission fluid and it did have a slow/jerky 1-2 and 2-1 shift. Especially in cold weather. I updated the Transmission Computer (TCU) and that seams to have made the shifting better. I will eventually get around to replacing the trans filter and fluid but for now it's perfectly fine. Still on original trans mounts as well. While i was there i also updated the Power Control Module (PCM) and Body Control Module (BCM) just to make sure all the firmware was up to date.

 

[N7turbo]

Additionally, during cold starts in the morning, the car violently jerks/lunges forward the very first time I apply the brakes while moving.

To be clear, are you throwing it into drive during the 30-second high idle?

concerning 'hard clunk' I feel during gear changes at low RPMs (1,000–1,500 range), particularly in stop-and-go traffic

Can you confirm which gears you are using?

 

[Faheem_23]

I mean i have a 2014 with 131k miles and the original transmission fluid and it did have a slow/jerky 1-2 and 2-1 shift. Especially in cold weather. I updated the Transmission Computer (TCU) and that seams to have made the shifting better. I will eventually get around to replacing the trans filter and fluid but for now it's perfectly fine. Still on original trans mounts as well. While i was there i also updated the Power Control Module (PCM) and Body Control Module (BCM) just to make sure all the firmware was up to date.

Hi! Thank you for your reply. It’s a great relief to know that the issue is fixable. Can you share where you got the update from and how much were you charged for the transmission computer, pcm and bcm update? And are you worried about changing the transmission fluid at a high mileage as i have read that it can do more harm than good?

 

[Faheem_23]

To be clear, you are throwing it into drive during the 30-second high idle?


Can you confirm which gears you are using?

No i wait for atleast 2-3 minutes every time i start the car and then attempt to drive. I just put it into drive and but i think the jerk happens when it shifts from 2nd gear to 1st gear. It only happens that one time after each start.